Grow Q&A: Why Is My Pot Growing Medium Turning Green?

Dear Dan, I’m using coco as my medium to grow in, but I’m noticing the top layer of the mix is going green. Is that something I should be worried about and how can I stop it? — Nathan

Dear Nathan,
The surface of your growing medium is green because it is covered in algae. This fungus grows where water meets light and can cause you problems with your plant (besides just being gross and ugly to look at). Cover your growing medium with something waterproof and opaque—white plastic is best as it helps reflect back some light onto your lower growth. If you keep the light from reaching the wet medium, you will rid yourself of your algae issues.